1. Field of the Invention
The invention relates to the generation of homogeneous mixtures and in particular to a process and mixture-generating apparatus for continuously generating homogeneous mixtures of freely selectable composition in a mixing chamber with an inlet, a feed pipe, a rotary fuel distributor and a mixture outlet.
It further relates to the supply of internal combustion engines with ignitable fuel-air mixtures by external mixture formation, particularly of Otto engines, as well as a control system, which is particularly provided for supplying Otto engines with lean fuel-air mixtures.
2. Discussion of the Background of the Invention and Material Information
Various types of apparatus have been proposed for producing ignitable fuel-air mixtures, and the following patent publications are cited for example in this connection: U.S. Pat. Nos. 4,353,848, 4,469,075, GB 1,588,856, DE 2 809 066 A1, DE 3 024 181 A1, WO 84/03735 A1, WO 83104282 A1, WO 85/00412 A1, CH 663823, CH 606784, EP 0209073 A2 and EP 0208 802 A1.
However, under variable operating conditions, meeting the conditions for efficient combustion by very fine division of the fuel and uniform mixing with the combustion air is particularly problematic inasmuch as the required composition cannot be ensured under transient operating conditions, when uncontrolled amounts of fuel are carried along with the fuel mixture.
That is why efficient fuel control with strongly variable air quantities on one hand and the use of technical means which are as simple as possible on the other hand are of critical importance for trouble-free continuous operation of motor vehicles in the entire operating range.
Motor vehicles with gasoline-engine propulsion are currently provided with the known three-way catalyst as standard equipment in order to meet the legal provisions regarding the admissible limits for emission of pollutants.
The so-called lean-burn engine concept is moreover mentioned within the framework of constant discussions regarding measures for reducing the emission of pollutants. The operation of gasoline engines with lean fuel-air mixtures with significant excess air according to the lean-burn concept offers the possibility of reducing the emission of pollutants and at the same time reducing fuel consumption. The fuel consumption of the gasoline engine could thereby be optimized.
The interest in the development of so-called lean engines or lean-mixture engines, i.e. Otto engines which operate with above-stoichiometric air/fuel ratios (Lambda values significantly greater than 1) is clearly apparent from numerous publications.
An article by G. Lech and V. Harms in the technical journal "Motortechnische Zeitschrift", 47 (1986), p. 423-427, relates to the problems of lean combustion under variable air conditions (Lambda values up to 1.7).
The requirements for operating motor vehicles with lean-burn engines are, however, very strict and partly contradictory.
Investigations in the framework of the present invention now have shown that the potential advantages of the lean-engine concept for the operation of Otto engines with lean mixtures with high excess air can only be achieved when no layer-charge combustion or twist combustion similar to layer-charge combustion occurs, i.e. when the combustion takes place uniformly in the entire operating range of the engine. Only in this way can it be achieved that the engine temperature in the advancing flame front is uniform, hence homogeneous and does not present any peak values as a result of non homogeneous charge distribution in the combustion chamber.
It is an object of the invention to ensure, through relatively simple and reliable technical means, the continuous formation of homogeneous mixtures of freely selectable composition, particularly ignitable fuel-air-mixtures and efficient mixture control with reduction of the emission of pollutants and fuel consumption.
A further object of the invention is to ensure, under all required operating conditions and particularly under transient operating conditions, automatic control of mixture formation by the finest possible fuel distribution as well as uniform mixing with the combustion air at variable air flow rates.
The invention further has the special object of ensuring the supply of internal-combustion engines with lean mixtures which are homogeneous and have a freely selectable composition with as high excess air as possible, in order to thereby particularly guarantee optimal operation of Otto engines in their entire operating range.